Section 2: Metabolic Diseases of Ruminants: Hypocalcemia (Donovan)

Question 1

metabolic disease

Answer 1

derangement of metabolic process

Question 2

milk fever =

Answer 2

hypocalcemia

Question 3

predisposing factors for hypocalcemia in cows

Answer 3

> 4 yrs old
high milk production
inappetence
low exercise
high stress (i.e. calving, hormonal changes)
Jersey breed
prepartum diet high in Calcium or has a positive DCAD

Question 4

When does HC usually occur?

Answer 4

at parturition. Ca requirement surges just prior to parturition, and more Ca is taken up from blood pool for lactational demand. Results in loss from bone, urine, fetus

Question 5

During HC, there is decreased Ca input from:

Answer 5

• Bone (older cows and/or +DCAD)

- Diet (decreased intake or absorption)

Question 6

3 hormones/vitamins involved in Ca metabolism*******

Answer 6

1) PTH (+)
2) Vit. D (+)
3) Thyrocalcitonin (-)

Question 7

What happens if pre-partum diet is high in Ca? ***

Answer 7

thyrocalcitonin is upregulated, which inhibits bone mobilization of Ca. Also inhibits PTH, so bone mobilization and intestinal absorption of Ca cannot be activated. Activation of active form of vit. D in kidney is inhibited.

Question 8

How is vit. D from sun transformed in the body?

Answer 8

turned into inactive form in liver, then active form is produced in the kidney under influence of PTH

Question 9

fx of active vit D

Answer 9

increases absorption of Ca and bone mobilization

Question 10

clinical signs of early stage milk fever

Answer 10

• off feed
• staggering
• protrusion of tongue
• normal temp
• fast HR

Question 11

excitement stage of milk fever

Answer 11

• severe ataxia
• muscle tremors
• dilated pupils
• faster HR
• dry/scant feces
• rumen stasis
• body temp variable

Question 12

recumbent stage of milk fever

Answer 12

• sternal recumb.
• loss of reflexes
• S neck (unique to milk fever!)
• fast HR
• temp variable

Question 13

unconscious stage of milk fever

Answer 13

• lat. recumb.
• groaning
• bloat!
• no reflexes
• HR 100-120, weak

Question 14

Ddx of milk fever

Answer 14

• no test
• good PE
• response to tx: calcium salt IV (preferred) or oral calcium gel

Question 15

HC prevention

Answer 15

Dietary manipulation during last 3 wks of gestation:

1) Ca restriction (trad. method) or
2) negative DCAD

Question 16

result of Ca restriction physiologically ***

Answer 16

No calcitonin produced, so PTH not inhibited. PTH stimulates bone mobilization of Ca and stimulates kidney to make active vit. D which also promotes bone mobilization and intestinal absorption of Ca

Question 17

DCAD =

Answer 17

(Na+ + K+) - (Cl- + S-)

Question 18

normal cow diets are neg/pos. charged

Answer 18

pos

Question 19

how does neg. DCAD prevent milk fever? ***

Answer 19

• induces mild metabolic acidosis
• decreased pH upregulates of PTH receptors in kidney, so it takes less PTH to induce reaction to transform inactive vit. D to active vit. D
• cow also releases bone buffer, which helps maintain Ca lvls in the blood by drawing out Ca with it

Question 20

anionic salts you can add to diet to make neg. DCAD

Answer 20

MgSO4, CaSO4, CaCl2, MgCl2, NH4Cl

Question 21

HC is a major risk factor for all of the following cattle diseases:

Answer 21

• prolapsed uterus
• retained placenta
• early metritis
• rumen stasis
• ketosis
• DA
• peripartum immune dysfunction
• down cow syndrome

Question 22

REVIEW SLIDE 35 FLOWCHART

Answer 22

:)

Question 23

insufficient dietary effective fiber can cause:

Answer 23

rumen acidosis, lameness, DA

Question 24

decreased DMI around calving can cause:

Answer 24

neg. energy/protein balance –> ketosis/fatty liver

Question 25

stages of HC in order

Answer 25

1) early stage
2) excitement stage
3) recumbent stage
4) unconscious stage